Over Revving

[Frazer 0]

Hi folks, I'm new to VR6's but not to vee-dubs, had several air-cooled and a couple of Golf's in the past.

Bought myself a lovely N reg VR6, basic model in mint condition at 113K miles.. Love the torque, love the delivery, love the understated looks (she's de-badged in cadbury metallic purple), not so keen on the soft suspension but hey, its a completely stock car.

I have an engine problem which has materialised after cleaning the throttle body. I had the TB cleaned as at idle the revs were not settling properly after warm up - nothing too much, just wavering around the 900 to 1000rpm. Now the engine is ok at idle but over revs when in gear with no gas. e.g. I'm in say 4th and the car will pull without any throttle at around 1700rpm. It is as if the engine is over compensating when under slight load. Reconnecting the TB plug improves the problem but only for a short period.

I'm new to such an advanced engine, having a better understanding of pots, pistons, and carb type tuning. Any ideas?

Do I need to replace the throttle body? If so what's the damage? Same on the air mass meter? Any other likely faults?

[DundeeDub 0]

check that the throttle cable is fitted properly and has not slipped over the grove over the side of the black plastic curved thing, you'll know what i'm on about when you see it

[Russ_vr6 12]

i would also suggest that it sounds like a poss vacuum leak,chck that the tb is tighened up and the gasket isnt sitting funny mate

sounds like unregulated air getting in to me

[Frazer 0]

Ok, so everything is tight and connected correctly. What is weird is that when I disconnect, re-connect the cables to the TB - the problem impoves then gets worse again which leads me to believe that the problem is internal to the TB.

What is the cost of a new TB?

Is this a DIY job?

Also, what role does the air mass meter play - should I replace it?

[FishWick 21]

An N reg could be OBD2. Does yours have an idle valve? If not then it's OBD2, in which case the throttle position sensor could be worn. The bad news on OBD2 is the throttle is a sealed unit and costs £250+VAT from VW!

If it's OBD1, you can replace the throttle sensor. £40 from VW.

Sounds like the ECU is readapting itself everytime you remove and replace the plug, hence the short lived improvement.

Find out if it's OBD1 or 2 first.... there's a sticky thread about it somewhere.

[Frazer 0]

Looking at the stickt thread on throttle bodies - I'm pretty sure I have an ODB2.

Do other suppliers (e.g. German & Swedish) sell TB's? Is there a cheaper option than VW?

Also, is replacing the TB a DIY job?

[VR6Pete 1,455]

http://www.vr6oc.com/e107_plugins/forum/forum_viewtopic.php?118088 Here is that thread.

[Frazer 0]

So I checked out the cost of getting a new TB - around £350 from VW..

My local VW spares shop however can get them straight from the manufacturer for £168 plus VAT. Do you guys think that it is worthwhile replacing the TB? Note that I have had the TB cleaned and re-calibrated by my VW approved mechanic, and still have the over revving issue.

[dellert 0]

I had a similar problem on my mk2 carb, it was a stick throttle cable, used to have to hook my foot under the pedal to kill the revs. When you say you disconnect the cables do you mean the throttle cable or you tlaking about electrcal wires?

[Frazer 0]

The electical cables to the throttle body. The throttle body is much different to a carb on a Mk2. My problem isn't so much a stuck throttle, more like the ECU is over compensating when the engine is under load.

[dubberVR6 0]

Would a Vag-Com diagnostic not pick up if it was a problem with the TB?

[Dave Lea 4]

depends who is reading it

[dubberVR6 0]

Ok............. It might be worth the small investment first though.

[Frazer 0]

What is a Vag-Com reader? Is that the fault code device that plugs into the dash by the lighter?

[FishWick 21]

VAG-COM is a bit more than that, it translates the error codes for you and runs from a laptop/PC.

OBD2 ECUs can be forced to adapt the throttle and you can also check it's operation in the measuring blocks.

Shame you're so far away otherwise I'd check it over for you.

When you turn the igntion on for the first time, can you hear the throttle making a high pitched whine and clonk a couple of times? This is the adaptation process. If it's silent, it indicates a problem!

[Frazer 0]

On start up the car revs to about 1800rpm then wavers a bit before settling to around 1000-1100rpm for a couple of mins then down to 900.

The issue is when the engine is warm and I've accelerated in any gear - after I come off the gas, the revs stay between 1700 to 2000, thus pulling the car on the flat. Out of gear the car gradually comes back to idle around 900.

I've got a good deal on a new throttle body, should be able to get it fitted & calibrated all in for about £200. As the car has done 114K now, that might be wise huh?

Thanks for the offer of the VAG-COM

[FishWick 21]

Fitting takes about 30 mins and no need to calibrate it, it does that itself. Just switch the ignition on to position 2 and leave it for about 30 seconds. Then you'll hear the noises I explained earlier as it sets itself.

Give it a bash and see how you get on.

[lee060 3]

depends who is reading it

folowing on this , code may not come up in all cases , but . thru good data readings out codes , all depends , if say the person carrimg out the faults can be found with test can be arsed , also if thye know what there looking for

, all i can say is dont depend on codes . read the data readings and see if everythings in check

[Frazer 0]

Over revving issue now solved. Sorted compeletely by replacing throttle body. Buying direct from Siemens VDO (OEM manufacturer) proved about 40% cheaper than sourcing part from VW (G&S don't stock them).

Got the old ODB2 TB if any one wants it for rebuilding, if that's possible.. 8-)